A Nassau County hardhat and diehard Big Blue fan says New York Giants quarterback Eli Manning broke his heart — by peddling a phony “game-worn” helmet that turned out to be a “$4,000 paperweight,” a new lawsuit charges.

Superfan Michael Jakab, 34, of Floral Park – who has a Giants tattoo on his arm and a team flag on his lawn — forked over $4,300 for a helmet Manning supposedly wore during the team’s 2007 Super Bowl season.

But shortly after the December 2013 purchase from another collector, Jakab grew suspicious when he could not “photomatch” the helmet with any pictures of Manning over several seasons, the suit states.

He also discovered “it was missing the swatches of Velcro that are supposed to be next to the earholes on all quarterback helmets” to hold radio receivers so QBs can hear their coaches, according to the suit, filed by Attorney Brian Brook, who had also filed a similar suit on behalf of another fan earlier this year.

“I knew something was wrong when it didn’t have the Velcro inside,” Jakab told The Post Tuesday.

“Also, the number of marks on it, there are a lot, just too many scratches. I tried to match it to three seasons worth of photos. There are a hundred images of Eli in every game and I went through every one. I couldn’t match to one of them,” Jakab said.

The lawsuit, filed July 25 in New Jersey Superior Court in Hackensack, also names the team, equipment manager Joe Skiba and Steiner Sports as co-defendants.

Like the earlier suit – which remains pending in federal court in New Jersey – it claims that Manning and Skiba conspired to sell the phoney merchandise to Steiner Sports, which then knowingly passed it along to unsuspecting fans.

That suit, filed by Brook in January on behalf of collector Eric Inselberg, charged that the Giants and Steiner sold dozens of fake items – including a Manning helmet on display in the Pro Football Hall of Fame.

The Giants have vigorously denied the allegations.

“We typically do not comment on pending litigation. However, in this instance, we do think it’s important to note that this suit is a publicity stunt by Eric Inselberg’s attorney, who had previously filed a groundless lawsuit which we have moved to dismiss,” spokesman Pat Hanlon told The Post Tuesday.

“We are confident that press coverage will be the most they achieve from their efforts, and we will defend this case vigorously to conclusion.”

But Jakab insists he was conned when he bought the helmet from a collector, who had bought it from another fan who originally purchased it from Steiner.

“Everyone trusts Steiner and I did. I got a top of the line [helmet], signed by Eli, with all the paperwork and the tamper proof seal, and I still got duped. Are these bulls–t helmets? Yes, I got a bulls–t helmet,” he fumed.

“To fans, I would say do your homework. Compare game-worn gear to the photos.“

He said he will always be a Giants fan, but Eli would be a different story if it comes out in court that he was in on the scam.

“If it turned out that dumbfounded look on his face is just a snake behind the blinds, I’d feel horrible and hope he got sacked in every game this season,” Jakab said.

His lawsuit seeks three times the $4,300 Jakab paid for the helmet, legal fees and “further relief as the Court may deem just and proper.”